Method and apparatus for powdered metal deposition by oxy-fuel gas flame



Mgrch 26, 1957 Filed-Feb. 9. 1953 A. I LONG' ET AL 2,786,779

METHOD AND APPARATUS FOR POWDERED METAL DEPOSITION BY OXY-FUEL GAS FLAME2 Sheets-Sheet l ATTORNEY March 26, 1957 LON ETAL METHOD AND APPARATUSFOR POWDERED METAL DEPOSITION BY OXY-FUEL GAS FLAME Filed Feb. 9, 1953 2Sheets-Sheet 2 fl/fred Black/00k ATTORNEY nited States Patent METHOD ANDAPPARATUS FOR POWDERED METAL DEPOSITION BY OXY-FUEL GAS FLANE AndrewLong, Camhe'rwell, London, Frederick Noel Taylor, Thornaby on Tees, andAlfred Blaeklock, (Tamberwell, London, England, assignors to Dewrance &(30., Ltd., London, England, a British company Application February 9,1953, Serial No. 335,822

13 Claims. (Cl. 117-22) This invention relates to processes andapparatus for flame deposition of metal powder onto one or more basemetal parts for increased resistance to corrosion or wear, to form awelded joint, or for other special purposes.

The art to which the present invention generally relates is known asmetal spraying. This term normally connotes a process of projectingglobules of molten metal by means of a carrier gas at the surface to becovered, these globules solidifying as individual particles afterdeposition on a relatively cold base metal surface. Such molten globulesmay be formed by melting the coating metal by a high temperature heatingflame, an electric are, or equivalent arrangements, this meltingoperation fusing and superheating the coating metal during orimmediately prior to its projection onto the surface to be coated.

In such metal spraying processes, the coating metal may be supplied tothe heating flame or electric are either in the form of a rod or wire orin the form of a metal powder. In known arrangements of the latter type,the metal powder is fed by a stream of compressed air or gas into astream of mixed oxygen and fuel gas discharged from a nozzle, theoxy-fuel gas mixture being ignited at the nozzle to provide the meltingflame. Where a flame melting and spraying blowpipe is employed, thedischarge tip of the blowpipe is normally held a considerable distancefrom the surface to be sprayed, i. e. a distance on the order of six toeight inches, so that there will be a prolonged contact between themetal to be deposited and the flame and yet the powder melting flamewill not be in effective heat transfer contact with the surface beingsprayed. The stream of compressed carrier air or gas is intimately mixedwith the oxy-fuel gas flame, causing the metal powder to be melted andthence projected in molten form onto the surface to be coated. As eachmolten globule tends to be flattened by its impact against the surface,the resultant structure is one of small individual solidified platingshaving relatively large spaces therebetween, and is characterized byentrapped oxides resulting from the passage of the molten globulesthrough the air. Consequently the resultant plated structure is usuallyporous to an undesirable extent and only mechanically bonded to thesubjacent base metal surface.

The known methods of applying molten metal coating to a surface by meansof a stream of carrier air or gas generally require three separateoperations. The first step is a thorough cleaning of the surface to becoated, this being effected by sand blasting or the like in order toclean and roughen the surface. The metal coating is then sprayed ontothe surface in the form of fused and superheated metal globules carriedin a stream of air or gas under considerable pressure. After theapplication of the coating metal is complete, a high temperature heatingflame or electric arc must be played over the coated surface to causethe coating to adhere properly to the surface and to effect greateruniformity and continuity to the layer of coating material.

Such metal spraying processes have disadvantages which have detachedfrom their commercial application. One disadvantage is the fact that theapplication of the coating involves the three successive operating stepsmentioned above, requiring a substantial operating time. Anotherdisadvantage is the relatively complicated controls involved. Forexample, the oxygen and fuel gas for the heating flame must. becontrolled as to pressure, volume, and proportions, to provide thedesired type of heating flame. In addition, the stream of carrier air orgas must be similarly carefully controlled, as must also be the feedingof the metal into the carrier stream. In practice, it is very difficultto properly coordinate all of these factors, and proper coordination isa necessity if a coating with proper adhesion and relative freedom fromporosity is to be obtained. These factors do not make the processparticularly suitable for mechanization. The apparatus required forcarrying out such processes is usually bulky and cumbersome andaccordingly does not lend itself for use as a portable unit.

Another disadvantage is that known processes and apparatus using a.metal powder are limited to the coating of. a single metal surface, suchas hard facing operations and the like, and cannot be used successfully,for example, in the fusion weld uniting of the adjoining surfaces of apair of metal members. In commercial practice, such fusion welding withadditional filler metal supplied is still limited to the filler metalbeing fed to the welding. zone in the form of a wire or rod.

In accordance with the present invention, the foregoing disadvantagesare overcome in a novel manner, and a metal powder spraying method andapparatus is provided which is applicable both to the localizedsurfacing of a single metal surface and to the fusion welding of metalparts. The invention has the further advantages that no prior cleaningof the work surface'is ordinarily needed and the apparatus requiredconsists primarily of a standard portable oxy-fuel gas welding torchunit with certain additions.

In general, the invention method comprises the steps of firstmaintaining an oxy-fuel gas-heating flame, preferably of oxygen andacetylene in predetermined proportions, in effective heating relationwith the surface of the workpiece or workpieces to have metal appliedthereto until all of the surface area has reached a uniform red heat, i.e. at a temperature substantially below the base metal fusiontemperature. The heating flame is then concentrated on a predeterminedlocalized area of the base metal surface until this initial area reachesa sweating temperature, this term, as used herein, indicating a state ofincipient surface fusion of the base metal. During such heating, astream of air at atmospheric pressure is aspirated into the oxy-fuel gasmixture between an initial zone, in which the oxygen under pressure ismixed with a suitable fuel gas under pressure in predeterminedproportions to form a combustible gas mixture and a mixture ignitionpoint spaced from the mixing zone. When the initial surface area beginsto sweat, finely divided metal powder, from a suitable source thereof,is introduced at a substantially uniform rate by gravity into the streamof aspirated air, for carrying the metal powder into the combustiblemixture by the aspirated carrier air. It is highly important that theoxy-fuel gas blowpipe be positioned at a predetermined distance from thesurface of the base metal at which the tip of the high temperature innercone of the flame is slightly spaced from that surface while the outercone of the flame bathes the area immediately surrounding the localizedarea to be sprayed. The metal powder is carried by the combustiblemixture and carrier air through the inner cone of the heating flame andimpinged onto the heated surface while it is being bathed with the outerflame cone. The metal power particles face.

are thus heated to a temperature approaching but lower than the metalmelting point in passing through the flame and immediately afterdeposition are fused integrally with the incipiently fused local area ofthe work surface by the heat received by conduction from the subjacentand surrounding base metal surface areas and the continued heatingefiect of the flame. The operation is continued until a solid coating ofa predetermined thickness free from porosity has been fused on the basemetal sur- A molecular bond is formed between the base metal and thedeposited metal. No further treatment is necessary to smooth the surfaceof the deposited metal.

The heating flame is then progressively moved over an adjacentincremental surface area which has been raised to the sweatingtemperature by the outer portion of the melting flame and the metalpowder is impinged against and fused therewith as described. The coatingoperation may by cyclically repeated as a continuous operation until asmooth uniform coating of the desired thickness has been built up on thebase metal. This coating may be either a facing on a single metalsurface or may form a. weld deposit integrally uniting two or more metalsurfaces.

For a better understanding of the invention method and apparatus,reference is made to the following detailed description of a typicalembodiment of the apparatus and a typical application of the method, asillustrated in the accompanying drawings. In the drawings:

Fig. 1 is an elevation, partly in section, of apparatus embodying theinvention;

Fig. 2 is a sectiontaken on the line 22 of Fig. 1;

Fig. 3 is a diagrammatic view illustrating the position of the blowpiperelative to the base metal;

Fig. 4 is an elevation of a modified construction of the blowpipe;

Fig. 5 is an enlarged exploded view partly in section of a portion ofthe construction shown in Fig. 4;

Fig. 6 is an end view, partly in section, of the powder control device;

Fig. 7 is an enlarged section on the line 77 of Fig. 6;

Figs. 8 and 9 are end views of certain parts taken 7 on the lines 8- -8and 9-9 of Fig. 5; and

Fig. 10 is a sectional view of a welded joint made in accordance withthe invention. 7

Referring to the drawings, the metal spraying apparatus of the inventionincludes an oxy-fuel gas blowpipe or torch which, except for the meansfor introducing the carrier air stream and entrained metal powder intothe oxy-fuel gas mixture, is of a well known construction. Thus, theblowpipe or torch 10 is illustrated as of the type commercially used foroxy-acetylene welding, including a mixer body or chamber having, at itsrear end, nipples 11 and 12 for attachment of the chamber 15 to separatesources of oxygen and acetylene under pressure, respectively. Valves 13and 14 are provided in converging flow passages in chamber 15 for thepurpose of controlling the volume of oxygen and acetylene, respectively,delivered to chamber 15, and thus the proportions of the resultantcombustible mixture leaving chamber 15. The latter is provided, at itsforward end, with a connecting pipe 16 internally threaded at itsforward end for attachment of a discharge nozzle or tapering orificemember 17. Nozzle 17 is progressively reduced in diameter from a pointintermediate its ends to its discharge end, as indicated at 18, itsouter surface along the forward end 18 being generally frusto-conical.The nozzle passage 17' forms a registering continuation of the passage16' in the pipe 16 and discharge opening from chamber 15.

The nozzle 17 is held in position in pipe 16 by an adapter member 20screwed into the forward end of pipe 16 and engaging the flanged innerend 19 of nozzle 17.

so as to provide an annular frusto-conical chamber 22 between thetapered forward end of nozzle 17 and the inner wall surface of chamber21. Nozzle 17 terminates short of the smaller end of chamber 21, and thelatter has a comparatively small diameter discharge orifice 23 axiallyaligned with nozzle 17 and registering with the nipple 24 of adownwardly curved connecting pipe or stem 25. Stem 25 is secured ontothe forward end of adapter 20 by a suitable coupling nut 26, and hasdetachably secured to its forward end the usual blowpipe discharge tipor nozzle 27 having a small diameter discharge opening at its lower end.

The metal powder to be deposited is contained within a supply hopper 30mounted on blowpipe 10. A cover 28 having an opening 29 therein for anatmospheric connection closes the top of the hopper 30. The hopper isfilled with a free flowing finely divided metal powder of the desiredmetallurgical composition. The hopper 30 has a conical bottom 31converging toward a central discharge pipe 32 by means of which thehopper is supported on a coupling member 35. In operation, the blowpipeis preferably so held that hopper 30 will be substantially vertical sothat the metal powder will flow by gravity downwardly through pipe 32.However, the device will operate satisfactorily even though hopper 30 isnot exactly vertical, and the center line of the latter may be atsubstantial angle to the vertical.

The coupling member 35 is formed with a central body portion 33 and endnipples 36 and 37. Extending axially of the body and nipples is acylindrical bore 34, concentric with the nipples. The body portion 33also has a radially extending threaded inlet passage 38 in its upperside communicating with bore 34, and having pipe 32 threaded thereinto.

Control of the flow of metal powder from hopper 30 into the couplingmember 35 is provided by means of a valve 40. Valve 40 consists of atubular stem 41 having a surface-to-surface fit within the rear end ofbore 34 and extending forwardly of the discharge end of pipe 32. Thestem 41 extends through a packing gland 42 threaded on nipple 36, and isprovided with a knurled head 45 having a reduced shoulder 44 fittingagainst gland 36. The central passage provided by the stem 41 iscontinued as a coaxial passage 43 opening rearwardly to atmospherethrough a knurled head 45.

The lower end of pipe 32 has its inner diameter progressively reduced toterminate in a discharge orifice 46. In a diametric zone aligned withthe axis of orifice 46, stem 41 is formed with a series ofcircumferentially spaced radial apertures 47. There are three of theseapertures, 47a, 47b and 47c, in the embodiment shown. although more orless than three may be provided, the sole criterion being that thecircumferential extent of stem 41 between adjacent apertures be at leastequal to the diameter of pipe orifice 46.

As shown in Fig. 2, the stem apertures 47 differ in flow area, aperture47a being the smallest and aperture 47c the largest. By positioning aselected one of these orifices in alignment with orifice 46 of pipe 32,the rate of flow of metal powder from hopper 30 into coupling 35 may bepre-selected. For this purpose, the knurled head 45 may be suitablymarked for cooperation witha locating indicia (not shown) on the outersurface of gland 42. The gravity fiow of metal powder may be interruptedor shut off by turning knurled head 45 to an ofi position where orifice46 is closed by an unperforated arc of the periphery of stem 41.

The forward nipple 37 of coupling member 35 is connected by a curvedpipe 50 to adapter 20. This pipe is connected by a gland 51 to nipple37, and by a gland 52 to a radial stem 53 on adapter 20. The pipe 50registers with a passage 54 arranged coaxially of stem 53 and V Adapter20 is formed with a forwardly tapering frustoconical chamber 21concentric with and surrounding in L closely spaced relation the forwardend 18 of nozzle 17 the annular chamber 22 of adapter 20.

communicating at its lower end with the rear portion of The reducedpressure created in the tapering annular chamber 22 by powder particlesimpinging thereon.

the high velocity flow of the combustible mixture under pressure throughpassage 21 and orifice 23 aspirates a flow of atmospheric air throughpassage 43, stem 41, bore 34, pipe 50, passage 54, and annular chamber22, into discharge orifice 23 of adapter 20. This stream of aspiratedair mixes thoroughly with the combustible mixture discharged from thenozzle passage 13 in the space 21 and the resultant mixture of oxygen,aspirated air and acetylene discharges from the orifice 23 through thepipe 25 and discharge nozzle 27. This gaseous mixture can be readilyignited at the discharge end of the tip pending on the composition andmelting point of the metal to be deposited, the valves 13 and 14 areoperated to secure the desired type of flame, e. g. excess-acetylene,neutral, reducing or oxidizing, a neutral flame being used for the lowertemperature nickel base alloys and an excess-acetylene flame for thehigh melting temperature cobalt base alloys.

When the blowpipe is to be used for metal deposition, the knurled head45 is turned from an off position to cause one of the apertures 47a, 47bor 470 to register with the pipe orifice 46. The atmospheric pressure onthe powder in the container 3% in conjunction with the stream ofaspirated air flowing past the lower edge of the registering aperture 47causes a steady stream of powder particles to be entrained in theaspirated air stream.

The physical character of the metal powder is highly important, if notessential, to successful operation of the blowpipe and process. Toinsure a steady flow of powder from the container into the aspirated airstream, the

powder should be in a freely flowable form. For this reason a finelydivided powder in the form of spherical or substantially sphericalparticles is preferred. The powder fineness should be substantially 100%through a 100 mesh U. S. Standard screen and a major portion between 100and 200 mesh. If most of the powder should be finer than 200 mesh, thereis a tendency for the powder to pack in the container and the powderflow be interrupted or an irregular stream of powder be entrained in theaspirated air.

In carrying out the process of the invention the hopper 30 is filledwith powdered metal of the physical character described and the type tobe deposited on the base metal surface and head 45 turned to an offposition. The powder aperture size, nozzle 17, and discharge tip 27 areselected to provide the most effective combination of parts. The oxygenand acetylene at a pressure of from 10-15 p. s. i., for example, arethen admitted to mixing chamber 15 through manipulation of valves 13 and14, and the combustible mixture ignited at the discharge end of nozzle27, the valves 13 and 14 being usually adjusted to provide a flame ofthe type normally used for welding operations, such as a neutral orslightly reducing flame. The blow pipe is then held as shown in Fig. 3with the tip 27 closely spaced, for example one inch or less, from thework surface 60 so that the inner or high temperature cone 61 of theflame has its tip at or slightly spaced from the work surface while theouter cone of the flame bathes the surface area surrounding the axis ofthe inner cone. The flame is moved over the work surface to be covereduntil the entire area has reached a uniform red heat. When thiscondition has been effected, the oxygen, acetylene and aspirated airflame is concentrated on an initial localized surface area until suchtime as this area is in a sweating condition. The resulting state ofincipient fusion of the base metal surface provides a sticky areacapable of holding any The valve 40 is then turned to position one ofthe orifices 47 in registry with orifice 46 of pipe 32, the particularorifice 47 being used being dependent upon the rate of powder depositiondesired. The atmospheric air entering passage 43 and drawn into annularpassage 22 by the aspirating action of the high velocity jet ofcombustible mixture issuing from nozzle 17, and entrained powder, mixeswith the combustible mixture in the space 21 and orifice 23. The powderparticles and aspirated air assume die velocity of the combustiblemixture while in the pipe 25 and dis charge therewith from the nozzletip 27. The powder particles are heated while in the high temperatureflame but due to the very short path of travel before the powderimpinges upon the sweating surface of the base metal, the powderparticles are heated in the flame only to a temperature approaching butstill below the melting temperature. As the powder strikes the sweatinglocalized surface area, with the blowpipe flame playing thereon, thepowder particles are caught on the surface of the base metal. The powderis rapidly fused and coalesced with the incipiently fused base metalsurface, due to the high flame temperature at the work surface and heatabsorption from the base metal. The outer cone of the flame spreads overthe area surrounding the localized area on which the metal powder isbeing deposited and heats those areas to a sweating temperature. Theblowpipe is then progressively moved over an adjoining area at asweating temperature and the described operation repeated until theentire surface of the base metal is covered.

In the modification illustrated in Figs. 4-9 a more compact constructionof blow pipe is illustrated. In this embodiment the body member isprovided with valves 13 and 14 controlling the flow of oxygen and fuelgas through separate passages 107 and 108 in the body member. As shownin Figs. 5 and 8, these passages terminate at opposite points in theconical end 116 of a threaded section 117 which fits into an adaptermember 11S leaving a forwardly tapering space 119 in which the oxygenand fuel gas mix before discharging through a central orifice passage120. The powder supply system is mounted directly on the adapter member118, as shown in Figs. 4-7, and consists of a covered container 30 forthe powdered metal which discharges through the conical bottom 31 andpipe 32 into the horizontal bore 134 of a stem 135 extending verticallyand then laterally from the adapter member. A tubular stem 141, havingcircumferentially spaced apertures 47 therein adapted to register withthe lower end of the pipe 32, controls the supply of metal powder to thebore 134 by various settings of the knurled head 145. The tubular stem141 is held in the various aperture registering positions by a springpressed ball 146 fitting into corresponding recesses 147 in the stem ata point longitudinally spaced from the apertures. The spring 148 is heldin position by a cap nut 149. The bore 134 communicates with a verticalpassage 150 in the stern 135, the lower end of the passage 15% beingbent at right angles and terminating in a boss 151 radially spaced fromthe recessed end of the orifice passage 120. A positioning pin 152projects at the opposite side of the orifice 126. The passages 120 and151) and pin 152 register with corresponding parallel passages and 161and a recess 162 respectively in a plug member 163. The plug member 163fits into a mixing chamber 164 of a barrel member 165, as indicated inbroken lines in Fig. 5, to define a forwardly tapering annular chamber166 in which the powder and carrier air discharged from the passage 161and oxygen-fuel gas mixture from the passage 160 are intimately mixed.The powder laden combustible gas stream discharges from the chamber 166through a central passage 167. The parts are held in their assembledposition by a sleeve member 170 and nut 171 engaging the forwardthreaded end of the adapter member 118. A curved pipe 125 having ashouldered fitting 126 and sliding coupling sleeve 127 is threaded onthe forward end of the sleeve member 170, and provides a conduit forconveying the powder-laden gas stream to the discharge tip 27.

The operation of the modified blowpipe construction shown in Figs. 4-9is substantially similar to that in the construction shown in Figs. 1and 2, the oxygen and a fuel gas, such as acetylene, being supplied incontrolled quantities to the mixing space 119 and the mixture deliveredthrough the central passage 160 to a discharge passage 167 at one end ofa tapered annular aspirating chamber 166, which causes a flow ofatmospheric air to be aspirated through the bore 134 and entrain thefinely divided powdered metal passing through aperture 47 from thecontainer 30.

The described process is particularly characterized by the fact that thepowder is not melted in passing through the heating flame. This has beenproven by tests in which the powder flow is initiated before the basemetal surface has reached a sweating temperature. In such case, thepowder particles projected against such surface area have been found tobounce off the surface,

and on examination clearly show that the powder particles are still in asolid unfused condition. The rapid melting of the powder after itsdeposition results from the surface being in an incipient fusedcondition and the high temperature of the heating flame.

In one example of the use of the process for hardfacing a block ofcarbon steel SA 212 with Coast Metals Inc. HN 23 alloy (a nickel basealloy containing boron and silicon), the HN 2B powder was successfullydeposited in a quarter inch layer on the base metal after the base metalhad been preheated to a sweating temperature of between 1100 and 1200 C.When the base metal surface was brought to a sweating temperature, themetal spray from the blow pipe readily deposited thereon and fused withthe steel. A smooth uniform surface was obtained on the deposited metalwith complete freedom from porosity and cracks and with a hardness of 61Rockwell C. Microphotographs of sections showed a solid layer of thedeposited metal on the carbon steel with a relatively thin fusion areabetween the boundary surfaces thereof.

The strength of the bond between the powder and the base metal, afterfusion has been effected, is of the order of at least 40.000 p. s. i.,thus indicating the presence of a strong molecular bond between thesurface and the metal 1 mixed in the desired proportions before beingplaced in the hopper 30. Alternatively, two or more hoppers could beconnected to the passage 54 of adapter 20 by suitable modification ofthe latter, with suitable proportioning valve apertures, such as 47.

As distinguished from known processes in which the powder is carried tothe base metal surface by a separate stream of air or gas under asubstantial superatmospheric pressure, the present invention is furthercharacterized by a powder flow in a given blowpipe which is regulatedprimarily by the pressure and velocity of the combustible gas mixture,since the rate of aspirated air flow through the coupling 35 forentrainment of powder therein is determined by the velocity of thecombustible mixture issuing from nozzle 18. Furthermore the metaldepositing operation is effected in one continuous step, and does notinvolve a plurality of separate operations, such as known methods offirst cleaning the base metal surface, then spraying molten metalthereagainst, and finally fusing the surface and deposited metal tocoalesce the deposited metal with the surface metal.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the inventionprinciples, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

l. A method of applying metal deposit to a metal surface comprising thesteps of mixing a combustible gas under controllable pressure with acombustion supporting gas under controllable pressure in a mixing zoneto form a combustible mixture under controllable pressure; igniting suchmixture at a point spaced from the mixing zone; maintaining theresultant controllable velocity flame in closely spaced effective heattransfer relation with such surface to elevate the temperature thereofto the incipient fusion temperature, while aspirating additional gasinto the mixture between the mixing zone and the ignition point; and,when the surface temperature attains the fusion value, controllablyentraining powdered metal, from a source of supply of the latter, intosuch additional gas for impingement onto the heated metal surface bysuch flame at a rate controlled by the pressure induced velocity of themixture.

2. A method of applying a metal deposit to a metal surface comprisingthe steps of mixing a combustible gas under pressure with a combustionsupporting gas under pressure in a mixing zone to form a combustiblemixture under pressure; igniting such mixture at a point spaced from themixing zone; maintaining the resultant flame in effective heat transferrelation with such surface to elevate the temperature thereof whileaspirating additional gas, at substantially atmospheric pressure, intothe mixture between the mixing zone and the ignition point; and afterthe metal surface has attained its incipient fusion temperature,entraining powdered metal, from a source of supply of the latter, intosuch additional gas for impingement onto the heated metal surface bysuch flame while continuing to play such flame on the surface.

3. A method of applying a metal deposit to a metal surface comprisingthe steps of mixing a combustible gas under pressure with a combustionsupporting gas under pressure in a mixing zone to form a combustiblemixture under pressure; igniting such mixture at a point spaced from themixing zone; maintaining the resultant flame in effective heat transferrelation with such surface to ele vate the temperature thereof to theincipient fusion value while aspirating atmospheric air into the mixturebetween the mixing zone and the ignition point; and, when thsurfacetemperature attains the incipient fusion value, en training powderedmetal, from a source of supply of the latter, into suchatmospheric airfor impingement out the heated metal surface by such flame.

4. A method of applying a metal deposit to a metal surface comprisingthe steps of mixing a combustible gas under controllable pressure with acombustion supporting gas under controllable pressure in a mixing zoneto form a combustible mixture under controllable pressure; igniting suchmixture at a point spaced from the mixing zone; maintaining theresultant controllable velocity flumi. in closely spaced effective heattransfer relation with su.h surface to elevate the temperature thereofto the incipient fusion value while aspirating atmospheric air into themixture between the mixing zone and the ignition point; and, when thesurface temperature attains the incipient fusion value, controllablyentraining powdered metal, from a source of supply of the latter, intosuch atmospheric air for impingement onto the heated metal surface bysuch flame at a rate controlled by the pressure induced velocity of themixture.

5. A method of applying metal deposit to a metal surface comprising thesteps of mixing a combustible gas under pressure with combustionsupporting gas under pressure in a mixing zone to form a combustiblemixture under pressure; igniting such mixture at a point spaced from themixing zone; maintaining the resultant flame in closely spaced effectiveheat transfer relation with such surface to elevate the temperaturethereof to the incipient fusion value while aspirating atmospheric airinto the mixture between the mixing zone and the ignition point; andafter the metal surface has attained its incipient fusion 9 temperature,controllably entraining powdered metal, from a source of supply of thelatter, into such atmospheric air for impingement onto the heated metalsurface by such flame, While continuing to play such flame on thesurface and on the powdered metal on the latter.

6. A method of applying metal deposit to a metal surface comprising thesteps of mixing a combustible gas under controllable pressure with acombustion supporting gas under controllable pressure in a mixing zoneto form a combustible mixture under controllable pressure; igniting suchmixture at a point spaced from the mixing zone; playing the resultantcontrollable velocity flame in closely spaced effective heat transferrelation over all of such surface to elevate the temperature thereof toa red heat while aspirating atmospheric air into the mixture between themixing zone and the ignition point; when the surface has attained a redheat, maintaining the flame in closely spaced effective heat transferrelation with a localized surface area to heat the latter to theincipient fusion temperature; after such localized surface area hasattained its incipient fusion temperature, controllably entrainingpowdered metal, from a source of supply of the latter, into suchatmospheric air for impingement onto the localized surface area by suchflame at a rate controlled by the pressure induced velocity of themixture, while continuing to play such flame on the localized surfacearea and then progressively impinging metal powder onto succeedinglocalized surface areas as the latter are successively heated to theincipient temperature.

7. A method of applying a metal deposit to a metal surface comprisingthe steps of mixing oxygen under pressure with a fuel gas under pressurein a mixing zone to form a combustible mixture under pressure; ignitingsuch mixture at a point spaced from the mixing zone; maintaining theresultant flame in closely spaced effective heat transfer relation withsuch surface to elevate the temperature thereof to the incipient fusionvalue while aspirating atmospheric air into the mixture between themixing zone and the ignition point; and, when the surface temperatureattains the incipient fusion value, entraining powdered metal, from asounce of supply of the latter, into such atmospheric air forimpingement onto the heated metal surface by such flame.

8. A method of applying a metal deposit to a metal surface comprisingthe steps of mixing oxygen under controllable pressure with a fuel gasunder controllable pressure in a mixing zone to form a combustiblemixture under controllable pressure; igniting such mixture at a pointspaced from the mixing zone; maintaining the resultant controllablevelocity flame in closely spaced effective heat transfer relation withsuch surface to elevate the temperature thereof to the incipient fusionvalue while aspirating atmospheric air into the mixture between themixing zone and the ignition point; and, when the surface temperatureattains the incipient fusion value, controllably entraining powderedmetal, from a source of supply of substantially spherical powdered metalparticles of a fineness of substantially 100% through a 100 mesh U. S.Standard screen with a major portion between 100 mesh and 200 mesh, intosuch atmospheric air for impingement onto the heated metal surface bysuch flame at a rate controlled by the pressure induced velocity of themixture, while continuing to play such flame on the surface.

9. Apparatus, for applying a metal deposit to a metal surface,comprising, in combination, a blowpipe having a gas mixing chamber,means for connecting said chamber to a source of oxygen under pressureand to a source of fuel gas under pressure for mixing of the gases insaid chamber to form a combustible mixture under pressure, meansseverally controlling the flows of oxygen and fuel gas into saidchamber, and a combustible mixture discharge nozzle receiving thecombustible mixture from said chamber; an aspirator connected betweenand in communication with said chamber and said nozzle for flow ofthecombustible mixture therethrough from the chamber to the nozzle;conduit means directly connected at one end to said aspirator and havingits opposite end open to atmosphere for aspiration of atmospheric airinto the mixture flowing through said aspirator; and a container forpowdered metal having a discharge outlet connected to said conduit meansat a point spaced from said opposite end for entrainment of powderedmetal into the air stream aspirated into the combustible mixture, saidcontainer being vented to atmosphere above the level of powdered metaltherein.

10. Apparatus, for applying a metal deposit to a metal surface,comprising, in combination, a blowpipe having a gas mixing chamber,means for connecting said chamber to a source of oxygen under pressureand to a source of fuel gas under pressure for mixing of the gases insaid chamber to form a combustible mixture under pressure, meansseverally controlling the flows of oxygen and fuel gas into saidchamber, and a combustible mixture discharge nozzle receiving ,thecombustible mixture from said chamber; an aspirator connected betweenand in com munication with said chamber and said nozzle for flow of thecombustible mixture therethrough from the chamber to the nozzle; saidaspirator having a central passage connected to said mixing chamber anddischarging toward said nozzle, and an annular passage surrounding saidcentral passage, said passages intercommunicating at the discharge endof said central passage; conduit means directly connected at one end tosaid annular passage and having its opposite end open to atmosphere foraspiration of atmospheric air into the mixture flowing through saidaspirator; a container for powdered metal having a discharge outletconnected to said conduit means at a point spaced from said opposite endfor entrainment of powdered metal into the air stream aspirated into thecombustible mixture, said container being vented to atmosphere above thelevel of powdered metal therein; said conduit means, in the operativeposition of blowpipe, extending substantially horizontally past saiddischarge outlet, and said discharge outlet opening perpendicularly intosaid conduit means; and valve means controlling flow of the powderedmetal from said container into said conduit means.

11. For use with a blowpipe having a gas mixing chamber, means forconnecting said chamber to a source of oxygen under pressure and to asource offuel gas under pressure for mixing of the gases in said chamberto form a combustible mixture under pressure, and a combustible mixturedischarge nozzle receiving the combustible mixture from said chamber; anadaptor unit comprising, in combination, an aspirator having couplingmeans for connection to such chamber and to such nozzle for flow of thecombustible mixture therethrough from the chamber to the nozzle; conduitmeans directly connected at one end to said aspirator and having itsopposite end open to atmosphere for aspiration of atmospheric air intothe mixture flowing through said aspirator; and a container for powderedmetal having a discharge outlet connected to said conduit means at apoint spaced from said opposite end for entrainment of powdered metalinto the air stream aspirated into the combustible mixture, saidcontainer being vented to atmosphere above the level of powdered metaltherein.

12. For use with a blowpipe having a gas mixing chamber, means forconnecting said chamber to a source of oxygen under pressure and to asource of fuel gas under pressure for mixing of the gases in saidchamber to form a combustible mixture under pressure, and a combustiblemixture discharge nozzle receiving the combustible mixture from saidchamber; an adaptor unit comprising, in combination, an aspirator havingcoupling means for connection to such chamber and to such nozzle forflow of the combustible mixture therethrough from the chamber to thenozzle; conduit means directly connected at one end to said aspiratorand having its opposite end open to atmosphere for aspiration ofatmospheric air into the mixture flowing through said aspirator; acontainer for powdered metal having a discharge outlet connected to saidconduit means at a point spaced from said opposite end for entrainmentof powdered metal into the air stream aspirated into the combustiblemixture, said container being vented to atmosphere above the level ofpowdered metal therein; and valve means controlling flow of the powderedmetal from said container into said conduit means.

13. For use with a heating blowtorch for forming an oxy-fuel flame, aneductor unit for supplying powder to the flame, said eductor unitincluding coupling means for connecting the same to the gas mixingchamber of the blowpipe and being formed with a duct for the passage ofa stream of the mixed gases therethrough; a nozzle component formed witha bore included in such duct; a complementary component formed with abore coaxial with the bore of the nozzle component, said eductorcomponent embracing said nozzle component and the bore of the eductorcomponent forming, with the nozzle component, an annular space; conduitmeans directly connected at one end to such space and having itsopposite end open to atmosphere for aspiration of atmospheric air intothe mixture flowing through the duct; and a container for powder havinga discharge outlet connected to said conduit means at a pointspaced-from said opposite end for entrainment of powder into the airstream aspirated into such mixture, said container being vented toatmosphere above the level of powdered metal therein.

References Cited in the file of this patent UNITED STATES PATENTS

1. A METHOD OF APPLYING METAL DEPOSIT TO A METAL SURFACE COMPRISING THESTEPS OF MIXING A COMBUSTIBLE GAS UNDER CONTROLLABLE PRESSURE WITH ACOMBUSTION SUPPORTING GAS UNDER CONTROLLABLE PRESSURE IN A MIXING ZONETO FROM A COMBUSTIBLE MIXTURE UNDER CONTROLLABLE PRESSURE; IGNITING SUCHMIXTURE AT A POINT SPACED FROM THE MIXING ZONE; MAINTAINING THERESULTANT CONTROLLABLE VELOCITY FLAME IN CLOSELY SPACED EFFECTIVE HEATTRANSFER RELATION WITH SUCH SURFACE TO ELEVATE THE TEMPERATURE THEREOFTO THE INCIPIENT FUSION TEMPERATURE, WHILE ASPIRATING ADDITONAL GAS INTOTHE MIXTURE BETWEEN THE MIXING ZONE AND THE IGNITION POINT; AND, WHENTHE SURFACE TEMPERATURE ATTAINS THE FUSION VALUE, CONTROLLABLYENTRAINING POWDERED METAL, FROM A SOURCE OF SUPPLY OF THE LATTER, INTSUCH ADDITIONAL GAS FOR IMPINGEMENT ONTO THE HEATED METAL SURFACE BYSUCH FLAME AT A RATE CONTROLLED BY THE PRESSURE INDUCED VELOCITY OF THEMIXTURE.